path-of-least-regret/lib/triangulate.js

Lightweight 2D polygon navmesh pathfinding: triangulation + A* + funnel + smoothing.

import { isCCW, triArea2 } from './math.js';
export function triangulate(simplePoly){
  const n = simplePoly.length; if(n<3) return [];
  const verts = simplePoly.slice(); if(!isCCW(verts)) verts.reverse();
  const result=[]; const Vlist=verts.slice();
  function insideTri(p,a,b,c){ const b1=triArea2(p,a,b)<0, b2=triArea2(p,b,c)<0, b3=triArea2(p,c,a)<0; return (b1===b2)&&(b2===b3); }
  let guard=0;
  while(Vlist.length>3 && guard++<10000){
    let ear=false;
    for(let i=0;i<Vlist.length;i++){
      const a=Vlist[(i-1+Vlist.length)%Vlist.length], b=Vlist[i], c=Vlist[(i+1)%Vlist.length];
      if(triArea2(a,b,c) <= 0) continue;
      let contains=false;
      for(let j=0;j<Vlist.length;j++){ const p=Vlist[j]; if(p===a||p===b||p===c) continue; if(insideTri(p,a,b,c)){ contains=true; break; } }
      if(contains) continue;
      result.push([a,b,c]); Vlist.splice(i,1); ear=true; break;
    }
    if(!ear) break;
  }
  if(Vlist.length===3) result.push([Vlist[0],Vlist[1],Vlist[2]]);
  return result;
}